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Is it a Meteorite?
They come to earth from outer space: ancient pieces of dislodged asteroids and planets that have passed through our solar system and eventually crashed on our soil. To discover one of these amazing space travelers is to hold something valuable in the hand that has never experienced human contact before. Just imagine what it has witnessed in its travels over the last 4.5 billion years. But is it really a meteorite or is it just an ordinary rock indigenous to planet earth?
Meteorites can come in a wide variety of shapes and sizes and their color can range from a rusty and pitted brown to an oxidized and smooth black or gray, or any combination there of. Obviously this makes their identification a difficult task, some samples even requiring some rather costly and time consuming tests. But don't despair as there are some simple field tests that you can perform on your own to help you to determine whether your discovery is just another ordinary rock from earth or a possible meteorite that has traveled through time and space.
The Hand Test
As you can see it is the specimen's overall density and consistency that will determine its shape and size and color when it eventually crashes into our soil. So this is the first thing we need to keep in mind when we're in the field examining potential discoveries. We need to hold the item in our hand so we can judge its density compared to its size and we also need to examine the item's shape and color. These are some of the first clues that can often suggest the item's true identity.
- Does the rock feel exceptionally heavy for its size? This might be hard to tell, but it’s only one possible characteristic.
- Is the rock pitted or dimpled?
- What is the rock's color makeup? A sample with a thin, dark crust (that’s different than the rest of the rock) could be a meteorite.
The Magnetic Test
A second test that can be performed in the field is the simple magnet test. Since meteorites generally possess a high metallic iron content they will likewise readily attract a magnet. Be sure to use a cheap, ceramic magnet and not a fancy rare-earth magnet. While this isn't a foolproof test it is a fairly reliable test when the suspected rock also possesses one or more of the attributes listed above. Just keep in mind that man has used iron to forge tools and utensils since the beginning of time and that slag and scraps from these past iron works is a fairly common discovery while in the field. Also keep in mind that in certain regions of the country nature iron deposits are quite common, which brings us to our next simple test.
The Tile Test
A third test that can be conducted in the field is the Tile Test. Basically, this just requires a simple piece of ceramic tile, like those that are laid in a bathroom or kitchen. These tiles have two sides, a glazed and smooth side and a rough unfinished side. You'll want to use the rough and unfinished side for this test. All you're going to do here is to use your rock in such a way that it creates a streak when dragged across the rough side of the tile. So when conducting this test you'll want to apply enough pressure to create a firm streak.
If your rock leaves a gray or black streak on the tile then your rock is not a meteorite. The same can be said if your rock leaves a reddish streak as this is a sign that your rock contains hematite, another mineral not found in meteorites. On the other hand, however, if your suspected rock leaves no streak on your ceramic tile then it is possibly a meteorite and it's time to move on to the next test.
The File Test
This next test requires a file and it is also going to require that you leave a scar on your suspected rock. Unfortunately this test must be conducted so that we can gather a better look at the inner skin of the rock. In most cases this scar won't hurt the potential of the rock.
If, after filing a spot of the rock flat, you can see small specks and/or streaks of shiny metallic material in the rock then you may have a meteorite. If the content of the rock doesn't have these streaks or specks then it probably isn't a meteorite. Most meteorites will contain these metallic properties.
And this is how you can test your suspected meteorites discoveries in the field. Unfortunately, the only way to achieve a 100% identification is by sending the suspected rock off to lab where they have the capabilities to conduct a more thorough and conclusive test. But more than likely, if your suspected space rock passes most of these basic tests, than it is likely that you have discovered a potentially valuable meteorite and an amazing piece of time and space. Hope this article helps, and, “Good luck out there!”
Thank you to the following experts for their help with this article:
Institute of Geophysics and Planetary Physics
Department of Earth, Planetary, and Space Sciences
University of California
Dr. Melinda Hutson, curator
Cascadia Meteorite Laboratory
Portland State University
Randy L. Korotev
Department of Earth & Planetary Sciences
Washington University in Saint Louis